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Subject[PATCH] PM / devfreq: Rewrite devfreq_update_status() to fix multiple bugs
Date
The current devfreq_update_status() has the following bugs:
- If previous frequency doesn't have a valid level, it does an out of bounds
access into the trans_table and causes memory corruption.
- When the new frequency doesn't have a valid level, the time spent in the
new frequency is counted towards the next valid frequency switch instead of
being ignored.
- The time spent on the previous frequency is added to the new frequency's
stats instead of the previous frequency's stats.

This patch fixes all of this.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
---
drivers/devfreq/devfreq.c | 31 ++++++++++++++++++++-----------
1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a0b2f7e..2042ec3 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -91,26 +91,35 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
*/
static int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
{
- int lev, prev_lev;
+ int lev, prev_lev, ret = 0;
unsigned long cur_time;

- lev = devfreq_get_freq_level(devfreq, freq);
- if (lev < 0)
- return lev;
-
cur_time = jiffies;
- devfreq->time_in_state[lev] +=
+
+ prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
+ if (prev_lev < 0) {
+ ret = prev_lev;
+ goto out;
+ }
+
+ devfreq->time_in_state[prev_lev] +=
cur_time - devfreq->last_stat_updated;
- if (freq != devfreq->previous_freq) {
- prev_lev = devfreq_get_freq_level(devfreq,
- devfreq->previous_freq);
+
+ lev = devfreq_get_freq_level(devfreq, freq);
+ if (lev < 0) {
+ ret = lev;
+ goto out;
+ }
+
+ if (lev != prev_lev) {
devfreq->trans_table[(prev_lev *
devfreq->profile->max_state) + lev]++;
devfreq->total_trans++;
}
- devfreq->last_stat_updated = cur_time;

- return 0;
+out:
+ devfreq->last_stat_updated = cur_time;
+ return ret;
}

/**
--
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